Public key cryptography (Asymmetric Cryptography, e.g. RSA) is a method of secure communication where one key is used for encryption and another for decryption. This method is heavily used in modern client-server transactions.
Biometric characteristic is an intrinsic characteristic of a person that is used to authenticate the person's identity: voice, fingerprint, retina scan, handwrite signature and so on. An authentication system tests whether the query biometric data is close or not to the stored biometric data associated with the claimed identity.
Authentication of a person is used in many business transactions including transactions over public networks such as the Internet. Despite numerous authentication schemes, neither privacy nor security is guaranteed in such transactions.